The microscope's lens is less than a third of a millimetre wide and fits inside a needle.

ABC News

Australian scientists have developed the world's smallest hand-held microscope, which is capable of detecting cancer cells often missed by surgeons during operations to remove breast cancer tumours.

Researchers at the University of Western Australia are using the microscope to capture 3D images using a tiny lens, less than a third of a millimetre wide, that fits inside a needle.

The device is now being tested on human tissue samples.

Associate Professor Robert McLaughlin says it could help prevent the trauma of repeat surgery in breast cancer patients.

"About one in four women who go for a lumpectomy - so that's where you take out the cancer and leave the rest of the breast - have to go back for more surgery because there are some cancer cells left in there," he said.

"The goal of our research is to make something to help the surgeons so that during surgery they can make sure they're getting all the cancer out."

Professor Christobel Saunders, a surgeon and breast cancer specialist at the Royal Perth Hospital, says it is particularly useful for looking at the edge of an area being operated on, to make sure no cancer cells are left behind.

"Tumours can produce very small areas just outside the main tumour mass that we simply can't see or feel," she said.

Professor Saunders welcomes the prospect of trials in operating theatres within two years.

"We really can see at a microscopic level where there is tumour. So it's almost like an ultrasound picture, but at a microscopic level," she said.

"The idea of this microscope in a needle is that we will be able to detect those at the time of surgery, and more effectively perform surgery."

Brain, lung surgeons interested in using needle technology

If successful, the needle microscopes could be rolled out in operating theatres around the world within a decade.

Associate Professor Robert McLaughlin says pathology testing will always be required after surgery to remove cancer, even if the needle microscope makes operations more accurate.

The quality of the images produced so far has drawn interest from surgeons looking at brain and lung disease.